A conventional vehicle incorporates a lead storage battery of which a rated voltage is 12V, as a battery for an electric device. Further, a large vehicle incorporates a battery of which a rated voltage is 24V. The battery of the large vehicle is formed by two of the lead storage batteries connected in series. The lead storage battery is charged by an alternator of the vehicle, and supplies power to vehicle load such as the electric device of the vehicle, a starter motor, or the like. Further, in order that the battery capacity (Ah) per volume or weight of the battery for the electric device is increased, the power source device for the vehicle connecting the auxiliary power storage device for the electric device, in which the lead storage battery and the nickel hydride battery or the lithium ion secondary battery are connected in parallel, has been developed (refer to patent literature 1).
In the power source device of patent literature 1, the lead storage battery electrically connected to an alternator and the auxiliary power storage device having the lithium ion secondary battery are connected in parallel. Additionally, in the power source device, since internal resistance or open circuit voltage of the lead storage battery or the lithium ion secondary battery is set so as to satisfy a predetermined condition, the lead storage battery and the lithium ion secondary battery are connected in parallel without through a DC/DC converter to reduce cost.
In the conventional power source having the auxiliary power storage device for the electric device configured of the lithium ion secondary battery which is connected in parallel with the lead storage battery, the lead storage battery is disposed at an engine room of the vehicle. The engine room easily receives the heat generated by the engine or other devices, or the heat from the outside air, and it is desirable that the auxiliary power storage device for the electric device is disposed at a place other than the engine room, being separated from the lead storage battery.
Then, the auxiliary power storage device for the electric device of the lithium ion secondary battery or the like is disposed, for example, on the floor under the seat in the cabin, utilizing a dead space (for example, refer to patent literature 2).